The case centres on more than 10,000 pupils who missed out on a C grade in GCSE English

Thousands of teenagers are awaiting a ruling from the High Court on Wednesday over the grading of GCSE English exams sat in June last year.

An alliance of pupils, unions, schools and councils is challenging changes in grade boundaries that saw many pupils getting lower grades than expected.

The High Court has taken evidence from the alliance, exam boards AQA and Edexcel and exams regulator Ofqual.

The judges' ruling is due to be revealed on Wednesday morning.

Giving evidence to the court in December, lawyers for the alliance said thousands of students had missed out on the grades they needed because of a last-minute "statistical fix".

They argued for the June exams to be regraded in line with those taken in January when the boundaries were lower.

But Edexcel and AQA said they had acted properly and Ofqual argued it had acted in a "clear, principled and transparent" way.

The challenge centres on more than 10,000 pupils who missed out on a C grade in GCSE English, which is a crucial benchmark used for entry into further education, vocational training and employment.

Up to 50,000 pupils in England, Wales and Northern Ireland could receive higher grades if the judges uphold the legal challenge.

Malcolm Trobe, deputy general secretary of the Association of School and College Leaders, said: "Whatever the outcome today, this was never about us, Ofqual or the awarding bodies.

"This action is about getting a fair outcome for the thousands of young people whose futures have been compromised by errors made by others. We hope they will be vindicated."

The case against the regulator Ofqual and exam boards AQA and Edexcel has been brought by a total of 167 individual pupils, supported by 150 schools and 42 councils, plus six professional bodies, including teaching unions.

Some 2,300 students who took exams set by the Welsh exam board WJEC in Wales have already been regraded on the orders of the Welsh government, which regulates exams set there.

In November, the exams regulator, Ofqual, published its findings after a review of the grading fiasco.

This concluded that January's GCSE English assessments, which accounted for about 10% of entries, had been "graded generously", but that the June boundaries had been properly set and that candidates' work had been properly graded.

Last year's English GCSE was a new qualification. Pupils started studying for it in September 2010 (the beginning of Year 10).

It was also a modular qualification, which meant pupils could take different components at different times, and in whatever order their school prefers. In effect it was a series of bite-size exams.

There was an external exam and also a controlled assessment, sat in the classroom under strict supervision and marked by teachers.

It is this element that appears to be at the heart of the problems with the English GCSE.